This invention relates to an alignment tool, and more particularly, to an alignment tool including a laser for detecting the alignment of precision alignment components, such as the pulleys of a belt drive system or in-line shafts of a transmission system.
In the past, pulleys of such systems have been aligned by the use of a cord line or a straight edge to indicate center alignment. Measurements must be taken accurately at four points on the pulleys; at the top, bottom and each side of the pulleys. Angular alignment requires the use of specialized gauges and instruments. These methods were less than completely satisfactory; since they are time consuming, are prone to inaccuracy, and unreliable because an adjustment of one alignment may cause the other alignments to change. Furthermore, these alignment procedures are relatively costly and require specially trained people.
U.S. Pat. No. 4,249,294 discloses an optical alignment tool which overcomes many of these limitations. The tool of this patent includes a target device releasably mountable to a pulley and an optical viewing device releasably mountable to another pulley. The optical viewing device has an eyepiece into which the user looks to view the target device. The target and optical viewing devices are mounted on interior portions of the pulleys which face one another so that the target device may be viewed through the optical viewing device. The target and optical viewing devices each have cross hairs which, when the pulleys are in the correct or preselected alignment, coincide with one another as viewed through the optical viewing device.
It may be possible to align the optical viewing device of U.S. Pat. No. 4,249,294 such that the cross hairs appear to coincide, when viewed through the optical viewing device, even though the webs of U-shaped members are oblique relative to the centerline between the pulleys. Such oblique relation may result from misalignment of the pulleys.
When viewing the optical viewing device of U.S. Pat. No. 4,249,294, the eye of the user must normally be reasonably close thereto requiring accessibility to the eye of the user. Additionally, the ability to view the target device through the optical viewing device while simultaneously adjusting the pulleys may be limited. Accordingly, alignment of the two pulleys by an individual user of the tool of U.S. Pat. No. 4,249,294 may entail an iterative process where the alignment is checked after each positioning of one or both of the pulleys.
Additionally, the optical viewing device of U.S. Pat. No. 4,248,924 may have sufficient weight to rotate the pulley on which it is mounted. Also, U.S. Pat. No. 4,248,924 does not disclose the addition of an electronic sensor to provide electrical signals indicative of when the cross hairs of the optical viewing and target devices coincide.